Drying drum for the drying of felts



O'ct. 20;...1- 942. w. THALER 2,299,662

I DRYING DRUM FOR THE DRYING OF F ELTS Filed March 13., 1940 2 Sheet's- Sheet 1 INVENTOR.

AN ATTORNEY.

Patented Oct. 20, 1942 DRYING DRUlVI FOR THE DRYING OF FELTS Wilhelm Thaler, Heidenheim-on-the-Brenz, Germany, assignor to American Voith Contact 00., Inc., New York, N. 1 a corporation of New York Application March 13, 1940, Serial No. 323,701 In Germany April 8,1939

3 Claims.

This invention relates to a drying drum working with blown-in air for the drying of endless cloth, especially for drier felts of paper machines.

The drier felts running in a paper machine need to be dried continually and most effectively and in the shortest possible tim to insure the most efficient dewatering of the paper web. Well-known devices work with blown or sucked air which as drying air is sucked or blown through the felts.

The present invention represents a drying drum with a fundamentally different air conduct, having the air channels arranged in the outer surface of the shell of the drying drum. These air channels arranged in the outer shell surface of the drying drum can be formed either as grooves parallel to the axis or as circumferential grooves.

If the air channels are grooves parallel to the axis the blown air is conducted to them through a fixed distributor on which the face of the drying drum glides. A special increas of the quantity of blown air or an increase of the velocity of the blown air within the channels takes place when arranging a distributor on both faces of the drum. In this case both distributors can be connected with a compressor or one of the distributors with a compressor and th other with a vacuum pump. This latter arrangement gives a possibility to conduct the air with very high speed along the felt evitating completely the formation of vapours at the same time by sucking off the damp air. This fact is especially very important for paper machines.

It is best to arrange the distributor heads with well-known devices by which the air conduct or the sucking off of the air may be limited to the sector covered by the felt.

If the air channels in the shell surface are circumferential grooves the blown-in air is conducted into channels by a hood arranged at the part of the shell which is not covered by the felt. To increase the air velocity in the circumferential grooves it is best to construct the hood in two parts, and to connect one chamber of the hood with a compressor, and the other chamber with a vacuum pump. This allows to conduct the drying air along the felt corresponding to the prevailing necessity either according to the principle of the current directed in the same direction of the running felt or according to the countercurrent principle.

The principle of the invention is shown on the drawings as follows:

Figure 1 shows a cross section of a drying drum with air channels on th outer shell parallel to the axis,

Figure 2 a longitudinal section through a part of this drying drum,

Figure 3 the joint between the drying drum and the fixed distributor head,

Figure 4 a longitudinal section through a drying drum with air channels in form of circumferential grooves,

Figure 5 a cross section of such a drying drum.

The drying drum after Figures 1-3 consists of the outer cylindrical shell I in which outer side the grooves 2 are machined parallel to the axis. The drying drum is covered by the felt 3 which is led by the rolls 45.

The faces of the drying drum are closed in by the covers 6 on both sides. These covers close in as well the journal in the centre and eventually a steam inlet pipe. The fac of the drying drum glides on the fixed distributor head 1 whose different channels 8 led in the air into the channels 2 of the revolving drying drum. Carbon rings III are arranged in circumferential grooves 9 to reduce the friction and to produce a tight joint between the face of the drying drum and the distributor head. In the inlets 8 special shutting off devices can be provided. By these means the size of the sector of the drying drum provided with air can be adjusted according to the surface covered by the felt.

The construction of the drying drum provided with air channels in form of circumferential grooves is shown on Figures 4-5. The circumferential grooves l2 are machined into the outer shell H. At its faces the drum is closed by the covers I3. Through the centre of this cover heating steam can be led in as well.

The inlet hood I6 is arranged between the running on side 14 and the running out side l5 and the felt web. This hood is connected on its fronts with air inlet or air outlet pipes respectively (I 'l) When the felt is running in the direction of the arrows as indicated at I l-l5 in Figure 5 the right chamber ll of the inlet hood is connected with the compressed air line and the left chamber with the vacuum pump. By these means the blown air is conducted along the felt according to the counter-current principle. The sucking off of the air by the left chamber increases firstly the air velocity in the channels, and secondly the air can be conducted to the outside and the formation of vapours at the machine is evitated.

I claim as new:

1. In a drying machine for drying band shaped fabrics like paper machine felts, the combination of a drum having a plurality of grooves on the periphery thereof formed by imperforate Walls, having inlet and outlet portions, said fabric being spaced from the grooves and resting on the intervening ridges thereof, air suction means removing the air at the outlet portions of the grooves, and air compressing means compressing air between the felt and the drum and into the inlet portions of the same grooves.

2. In a drying machine for drying band shaped fabrics like paper machine felts, the combination of a rotary drum having a plurality of circumferentially extending grooves on the periphery thereof formed by imperforate Walls, rotatable at least in one direction, said fabric being spaced from the grooves and resting on the intervening ridges thereof, and moving with the drum from the entrance side to the discharge side for the fabric, and suction means for removing the air in the grooves at the entrance side of the fabric, and means for supplying compressed air to the same grooves at the discharge side of the fabric, to increase the velocities of the air streams in the grooves, the air streams moving in a direction opposite to the direction of the drum.

3. In a drying machine for drying band shaped fabrics like paper machine felts, a drum having a plurality of grooves formed by imperforate walls of the drum on the periphery thereof, said fabric resting on the intervening ridges between the grooves to form therewith a continuous open duct, suction means inducing air at one end of the duct and compressing means at the other end of the duct for forcing air into said end of said duct, for drying the side of the fabric exposed to the grooves, said grooves running coaxially longitudinally of the drum.

WILHELM THALER. 

